The barrel can generally slide in its barrel holder between a rear firing position and a front loading position. Axial displacement of the barrel in its barrel holder is intended, inter alia, to return the piston to the rear firing position in the barrel for the next shot, the piston being situated at the front of the barrel after each shot, after having been driven there during firing.
The barrel is held in its barrel holder with the aid of a holding system which can be retracted in order to allow for disassembly of the apparatus.
The holding system has proven to be difficult to handle when disassembling the fixing apparatus.